1. Field of the Invention
The present invention relates to a Plasma Display Panel (PDP) and, in particular, to a PDP in which the shape, of transparent electrode layers is changed for high precision in shaping display electrodes.
2. Description of the Related Art
In general, a Plasma Display Panel (PDP) is a display device in which ultraviolet rays generated by a gas discharge excite phosphors to produce an image and has an advantage over a cathode ray tube due to its large screen with thin depth and high resolution.
In a typical Alternating Current (AC) PDP, discharge cells are defined by barrier ribs placed between a front substrate and a rear substrate. Corresponding to each discharge cell, address electrodes are formed on the rear substrate and display electrodes, comprising a sustain electrode and scan electrodes, are formed on the front substrate. The address electrode and the display electrodes are covered with respective dielectric layers. Each discharge cell has a phosphor layer with one of red, blue and green phosphors formed thereon and is filled with a discharge gas (generally, a gas mixture of Ne—Xe).
In such a PDP, a discharge cell for light emission is selected by the address discharge that occurs by an address voltage supplied between the address electrode and the scan electrode. Then, a plasma discharge takes place inside the selected discharge cell due to a sustain voltage (Vs) supplied between the sustain electrode and the scan electrode, and the plasma emits vacuum ultraviolet rays that excite the phosphor layer in the discharge cell to emit visible light to form an image.
For the operation of the PDP, the sustain electrode and the scan electrode are made of a transparent electrode layer, such as Indium-Tin Oxide (ITO), so that both electrodes can transmit the visible light generated by the discharge cell. The conductance of each transparent electrode layer is compensated for by a bus electrode layer made of a metallic material such as silver.
The following steps can be applied for forming the transparent electrode: (1) forming an ITO layer on the entire front substrate, (2) forming a mask layer on the ITO layer by a well known photolithography process, (3) etching the unmasked ITO layer and (4) stripping the mask layer and cleaning/drying. Alternatively, the following steps can be applied for forming the transparent electrode: (1) forming an ITO layer on the entire front substrate, (2) etching the ITO layer directly by laser using a wavelength of 1,064 nm for easy vaporization.
The transparent electrode layer of the PDP in the early period is formed in strip pattern, and characteristics of discharging in the discharge cell are influenced by only the line-width and the discharge gap thereof. In order to improve discharge efficiency, however, a new structure is recently introduced in which the line-width of the transparent electrode layer is reduced in the non-discharge region between the discharge cells while the line-width of the transparent electrode layer is increased in the discharge region of the discharge cell.
Also, there is an attempt to increase the discharge efficiency by changing the plane shape of the discharge cell into a polygon over than a rectangle. Accordingly, the transparent electrode layer of the display electrode has the variety in plane shape.
However, this complicated shape of the transparent electrode layer causes a problem in that its corners, compared with other line portions, has a high degree of roughness due to an increase in process variations during the patterning of the transparent electrode layer by wet etching or laser etching. That causes the deterioration of the precision level of shaping the transparent electrode layer, which leads to poor discharge characteristics, such as misdischarge and display failures such as image stains.